The present invention relates to an optical system in which a non-formula-specific modular afocal variator in combination with a supplemental lens system provides the optical system with both focusing means and active spherical and chromatic aberration corrective improvement for distant and near-focus. The combination of the modular afocal variator with the supplemental lens system produces a new type of integrated focusing device for optical systems that is itself a modular system.
Optical variators are typically used in optical systems to change the magnification of an image. For example, afocal variators have been used in projector lenses to alter the size of a projected image on a screen. In many instances, optical variator devices are used in combination with a front optical system or a rear optical system. In some instances they have even been used in combination with both a front objective system and a rear optical system. However, traditional optical systems which incorporate variator optical systems to alter the size of an image are not able to focus the image, and are usually only functional at relatively short back focal distances.
While the use of variators, either alone or in combination with either a front optical system or a rear optical system, are known, they largely are not known to have been used to alter active focal length so as to act as a focusing system as opposed to a system for altering image size at a fixed focal plane, such as a zoom lens. In the past where it has been desired to alter focal length, this has usually been accomplished by continuously or discretely changing the length of the optical system, or by changing the location or type of imaging lenses in the front, rear, or both front and rear optical systems. Generally the prior art has altered focal length by manipulating the imaging lens system, changing the length of the optical system, or changing the location or type of lenses in either the front or rear optical systems.
For example, Hillman (U.S. Pat. No. 2,937,570) discloses a telescope system in which the image forming lenses are moved in order to focus the system. Focusing is accomplished by moving the objective lens relative to the focusing lens, both of which are part of the telescope's “formula-specific” objective imaging system. Focusing is not accomplished or taught to be feasible by moving a central, modular position of an afocal variator, nor by determining the optical effect of an afocal variator and incorporating its front and rear elements into the image-forming optics, but still retaining a central modular element which is non-image-forming and essentially non-formula specific.
Matsumura (U.S. Pat. No. 4,318,585) discloses an optical system with an afocal focusing group, but in which the afocal focusing group is a Galilean telescope rather than an afocal variator. Furthermore, the system as taught by Matsumura does not incorporate the front, rear or front and rear elements of an afocal variator into the calculation and formulation of the image forming optics.
Quenderff (French Patent No. 2,572,545) teaches the use of a zoom lens to make enlarged pictures, and also teaches the use of various known mechanical devices for connecting together optical modules. However, it does not disclose the use of a central afocal variator module as a focusing element.
Margolis (U.S. Pat. No. 4,988,173), in contrast, teaches the use of a modular afocal variator optical system which can be used in optical instruments, such as long-distance microscopes, as the mechanism for providing focus. However, in this reference the modular afocal variator does not impart active spherical or chromatic aberration corrective improvement within the characteristics of the modular afocal variator itself. This modular afocal variator may in fact cause additional spherical and chromatic aberration.
While U.S. Pat. No. 4,988,173 teaches the use of a modular afocal variator as the focusing means of optical devices, it does not teach that under specific conditions the modular afocal variator can be supplemented with a lens system which can be positioned to impart active transitional spherical and chromatic aberration corrective improvement when incorporated in optical devices so as to provide focus and improved image quality over a range of far and near focal points. Additionally, the modular afocal variator of U.S. Pat. No. 4,988,173 has additional limitations, such as the functional size of the aperture of the optical system. What is needed is an improved modular afocal variator system that provides active correction of spherical and chromatic aberration and greater operational parameters.